1. Field of the Invention
The present invention relates to a water-based coated-type vibration damping material containing a resin emulsion and an inorganic filter, which is excellent in rigidity and vibration damping capability as well anti-blister capability, for use in a floor of a vehicle or the like.
2. Description of the Related Art
A sheet-shaped vibration damping material mainly composed of asphalt is disposed on a floor of a vehicle such as an automobile or the like in order to prevent vibration. However, in case of using such sheet-shaped vibration damping material in the vehicle or the like, the sheet material needs to be cut in conformity with a shape of an area on which it is laid and arranged. Then, a worker must place the cut sheet-shaped vibration damping material by hand. Thus, the conventional vibration damping material has become a bottleneck for automation and obstructed reduction of operation time. In view of such situation, as shown in Japanese Laid Open Patent Publication No. 2004-115665, there has been developed a coated-type vibration damping composition or a water-based emulsion for use in vibration damping that enables automation by a robot.
The publication No. 2004-115665 discloses an invention of a water-based emulsion for vibration damping material having a coagulation rate controlled within a fixed range. Where this emulsion is coated thickly as a vibration damping material and such thick coated layer is dried, the coated layer is dried and hardened from a surface. Then, it is prevented that a blister is produced or a crack is generated on the coated layer when water inside the coated layer evaporates. Thus, the emulsion improves a drying property of the coated layer formed as the vibration damping material.
The water-based emulsion for vibration damping material according to such conventional invention enables automation by robots and is able to shorten the operation time. Moreover, since the emulsion is a water-based coating material, it has also advantages that there are not generated any asphalt odor in conventional sheet-shaped vibration damping materials and any organic solvent odor in an organic solvent paint at the time of construction.
However, a propylene glycol is blended as an additive in 4.5% in the water-based emulsion for vibration damping material according to the publication No. 2004-115665. Therefore, if the coated-type vibration damping material is coated over a coated film of an electrodeposition paint provided on a vehicle body panel or the like and then baked, the propylene glycol swells and softens the electrodeposition film. Thereafter, when a hot water immersion is conducted thereon, the hot water invades the softened electrodeposition film so as to go into an interface between the electrodeposition film and a steel plate. Consequently, there are generated blisters or minute bumps or swellings on the electrodeposition film.
Such hot water immersion is easy to occur particularly in case a snow adhering to shoes is melted and warmed on a vehicle floor. Then, since water-based vibration damping coating materials often use a propylene glycol or ethylene glycol, there takes place a problem that blisters are generated on a base coated film of a vehicle or an electrodeposition film by the aforementioned mechanism.